As shown in FIG. 1, in Europe 230-240V line voltage halogen lamps today are in the lower range of the C class range close to the D class range boundary. However, B class efficiency is the most desirable. The application of an infrared reflecting coating to the lamp can improve lamp efficiency, so to reach the B energy class is theoretically possible.
There are several major requirements of the halogen lamp design with infrared (IR) reflecting technology developed to produce higher efficiency halogen lamps. IR reflectivity and visible transmission of the infrared reflecting multilayer should be increased. Bulb and filament shape should be optimized to reflect infrared radiation back to the filament as much as possible. Also, the filament should be maintained in the designed place, namely, in center of the bulb both during manufacturing and throughout its lifetime. Nevertheless, to reach B class is a huge step, even for low wattage lamps, where wire and coil dimensions are small. Small wire and coil size can easily cause the misfit and deformation of the filament during manufacturing and throughout its lifetime.